In June 2011, an international team of experts hoping to capture images of some of Borneo’s diverse wildlife, including the secretive Diard’s clouded leopard and the enigmatic orangutan, set up time-lapse camera traps within the Wehea Forest on the island’s eastern tip. What the scientists weren’t expecting was to capture photographic evidence of the existence of Miller’s grizzled langur, a primate thought to be extinct.

Miller’s grizzled langur, a large, grey monkey, is a subspecies of Hose’s langur. First described in Indonesia in 1985, the only images of this subspecies previously available were sketches based on museum specimens.

Fires, human encroachment, and the conversion of land for agriculture and mining all contributed to the destruction of the forest habitat upon which Miller’s grizzled langur depends. This destruction, combined with hunting pressures, led to the subspecies becoming so rare that it was widely assumed to have died out, with extensive surveys conducted in 2005 yielding no evidence of its continued survival.

Close analysis of the latest camera trap images from Wehea Forest has confirmed that the primates captured on film were, in fact, Miller’s grizzled langurs.

This subspecies was once found in the north-eastern part of Borneo, as well as the islands of Java and Sumatra, and the Thai-Malay peninsula. The news of the rediscovery of the subspecies came as quite a shock to scientists, given that Wehea Forest lies outside the previously recorded range of Miller’s grizzled langur.

Over a two-month period, more than 4,000 images were captured of Miller’s grizzled langur in Wehea Forest, a 38,000-hectare area of mostly undisturbed forest. However, scientists are as yet unsure how many individuals were photographed, as it is possible that one or two families kept returning to the area in which the cameras were hidden.

“East Kalimantan can be a challenging place to conduct research, given the remoteness of many remaining forested areas, so it isn’t surprising that so little is known about this primate,” says Dr Stephanie Spehar, Assistant Professor of Anthropology at the University of Wisconsin Oshkosh, USA.

The researchers are hoping that there may still be large enough populations of Miller’s grizzled langur in existence to ensure its future survival, and have returned to conduct more detailed observations of the monkeys.

The rediscovery of Miller’s grizzled langur is certainly positive news, and while it represents years of hard work and dedication on behalf of the researchers, it is likely that Miller’s grizzled langur is far from being safe, as PhD student Brent Loken from Simon Fraser University, British Columbia, Canada, explains, “While our finding confirms the monkey still exists in East Kalimantan, there is a good chance that it remains one of the world’s most endangered primates. I believe it is a race against time to protect many species in Borneo.”

The scientists will return to the area in order to conduct further studies on the population of Miller’s grizzled langur, and try to estimate how many individuals of the subspecies there are.

“It is difficult to adopt conservation strategies to protect species when we don’t even know the extent of where they live,” says Mr Loken. “We need more scientists in the field working on understudied species such as Miller’s grizzled langur, clouded leopards and sun bears.”